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BARD1 lee ubiquitinación de lisina 15 H2A para recombinación homóloga directa

Jordan R Becker^1,2, Gillian Clifford³, Clara Bonnet^1,2

¹Medical Research Council (MRC) Molecular Haematology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, UK.

|July 29, 2021

Resumen

El complejo BRCA1-BARD1 recluta a BRCA1 para las rupturas de doble cadena de ADN a través de un nuevo motivo que involucra modificaciones histónicas. Esta interacción es crucial para la reparación de la recombinación homóloga y antagoniza la vía 53BP1.

Área de la Ciencia:

Biología molecular
La genética
La bioquímica

Sus antecedentes:

La ubiquitinación mediada por RNF168 de H2A en las rupturas de doble cadena de ADN (DSB) es crítica para el reclutamiento de BRCA1 y 53BP1.
Si bien se entiende el reclutamiento de 53BP1 a través de H2AK15ub, el mecanismo para el reclutamiento de BRCA1 por RNF168 sigue sin estar claro.
Comprender cómo se recluta el BRCA1 es clave para aclarar la elección entre las vías de reparación de la recombinación homóloga y no homóloga.

Objetivo del estudio:

Identificar el mecanismo por el cual RNF168 promueve el reclutamiento de BRCA1 a los DSB.
Investigar el papel de BARD1 en el reclutamiento de BRCA1 y la recombinación homóloga.
Para aclarar cómo los complejos BRCA1-BARD1 coordinan la elección de la vía de reparación DSB.

Principales métodos:

Identificación de un motivo de reclutamiento dependiente de la ubiquitina (BUDR) en el BARD1.
Análisis de la interacción de BARD1 con las histonas ubiquitinadas (H2AK15ub) y la H4K20 no metilada.
Experimentos de epistasis genética que incluyen deleciones de RNF168 y 53BP1.

Principales resultados:

Un nuevo BUDR en BARD1 involucra a H2AK15ub para reclutar BRCA1 a los DSB.
La alteración del BUDR de BARD1 altera la recombinación homóloga y aumenta la sensibilidad a los inhibidores de PARP y al cisplatino.
BARD1 utiliza interacciones multivalentes con H2AK15ub y H4K20 para unirse a la cromatina y promover la función de BRCA1-BARD1.
El papel de unión de la cromatina de BARD1 es prescindible cuando RNF168 o 53BP1 están ausentes.

Conclusiones:

Los complejos BRCA1-BARD1 detectan los daños en el ADN y las modificaciones de las histonas posteriores a la replicación para gobernar la elección de la vía de reparación de DSB.
Las interacciones BUDR y multivalentes identificadas destacan un mecanismo para el reclutamiento de BRCA1 y la promoción de la recombinación homóloga.
Estos hallazgos establecen un paradigma de cómo BRCA1-BARD1 antagoniza la vía 53BP1 y promueve la recombinación homóloga.

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